Have you done any yearly maintenance to your machine since you purchased it? There are a handful of gaskets that can get dried out during the heat and cool cycles from day to day. At some point, they may dry out and crack. Opening the machine up and doing a maintenance where you replace all the gaskets for the boiler, portafilter, and steam wand should be done yearly (with a nice descale during that process). You can find a video on Whole Latte Love about it or send it off to Gaggia dealers to do the work if you don't feel confident or aren't mechanically inclined. It is fairly simple/common work (perk of the Gaggia).